Lateral retraction system for minimizing muscle damage in spinal surgery

ABSTRACT

A lateral retractor system for forming a pathway to a patient&#39;s intervertebral disc space includes a single dilator and a retractable dual-tapered-blade assembly. The dilator may feature a narrow rectangular body for insertion at an insertion orientation parallel to the fibers of the patient&#39;s psoas muscle, at an approximate 45-degree angle to the patient&#39;s spine. The retractable dual-tapered-blade assembly consists of only two blade subassemblies, each having a blade bordered by adjustable wings, along with built-in lighting and video capabilities. The dual-tapered-blade assembly may be passed over the single dilator at the insertion orientation and rotated approximately 45-50 degrees to a final rotated orientation parallel to the intervertebral disc space before the two blade subassemblies are retracted away from one another to create the surgical pathway, while simultaneously and continuously assessing for encroachment upon one or more nerve structures within 360-degrees of the instrument. Other embodiments are also disclosed.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

The application is a continuation-in-part of pending prior U.S. patentapplication Ser. No. 16/533,368, filed Aug. 6, 2019 by EdwardRustamzadeh for “LATERAL RETRACTOR SYSTEM FOR MINIMIZING MUSCLE DAMAGEIN SPINAL SURGERY,” which is a continuation of prior U.S. patentapplication Ser. No. 16/356,494, filed Mar. 18, 2019 by EdwardRustamzadeh for “LATERAL RETRACTOR SYSTEM FOR MINIMIZING MUSCLE DAMAGEIN SPINAL SURGERY” and issued as U.S. Pat. No. 10,426,452 on Oct. 1,2019, which is a divisional of prior U.S. patent application Ser. No.16/273,322, filed Feb. 12, 2019 by Edward Rustamzadeh for “LATERALRETRACTOR SYSTEM FOR MINIMIZING MUSCLE DAMAGE IN SPINAL SURGERY” andissued as U.S. Pat. No. 10,363,023 on Jul. 30, 2019, all of which patentapplications are incorporated herein by reference.

BACKGROUND

The spine is a flexible column formed of a plurality of bones calledvertebrae. The vertebrae are hollow and piled one upon the other,forming a strong hollow column for support of the cranium and trunk. Thehollow core of the spine houses and protects the nerves of the spinalcord. The different vertebrae are connected to one another by means ofarticular processes and intervertebral, fibrocartilaginous bodies, orspinal discs. Various spinal disorders may cause the spine to becomemisaligned, curved, and/or twisted or result in fractured and/orcompressed vertebrae. It is often necessary to surgically correct thesespinal disorders.

The spine includes seven cervical (neck) vertebrae, twelve thoracic(chest) vertebrae, five lumbar (lower back) vertebrae, and the fusedvertebrae in the sacrum and coccyx that help to form the hip region.While the shapes of individual vertebrae differ among these regions,each is essentially a short hollow shaft containing the bundle of nervesknown as the spinal cord. Individual nerves, such as those carryingmessages to the arms or legs, enter and exit the spinal cord throughgaps between vertebrae.

The spinal discs act as shock absorbers, cushioning the spine, andpreventing individual bones from contacting each other. Discs also helpto hold the vertebrae together. The weight of the upper body istransferred through the spine to the hips and the legs. The spine isheld upright through the work of the back muscles, which are attached tothe vertebrae.

A number of approaches, systems, and apparatuses have been devised toaccomplish a variety of surgical interventions in association with thespine. These approaches enable a surgeon to place instrumentation andimplantable apparatuses related to discectomy, laminectomy, spinalfusion, vertebral body replacement and other procedures intended toaddress pathologies of the spine. The variety of surgical approaches tothe spine have a number of advantages and drawbacks such that no oneperfect approach exists. A surgeon often chooses one surgical approachto the spine from a multitude of options dependent on the relevantanatomy, pathology, and a comparison of the advantages and drawbacks ofthe variety of approaches relevant to a particular patient.

A common surgical approach to the spine is the lateral approach, which,in general, requires a surgeon to access the spine by creating asurgical pathway through the side of the patient's body through thepsoas muscle to an intervertebral disc space where it is possible todock onto the lateral lumbar disc. Variants of the lateral approach arecommonly referred to as the “direct lateral” approach in associationwith the “DLIF” procedure, the “extreme lateral” approach in associationwith the “XLIF” procedure, and the “oblique lumbar” approach inassociation with the “OLIF” procedure.

A common problem associated with the lateral surgical approach includesa significant risk of damage to the musculature surrounding the spine.FIGS. 1A-1B illustrates a partial view of a spine 100 comprised ofsequential vertebrae 109, each separated by intervertebral disc space110, with an attached psoas muscle group 102 (including the psoas minorand psoas major). As shown, the psoas muscle 102 runs generally in acranial-caudal direction with muscle fibers attached diagonally or at anapproximate 45-degree angle to the spine 100. FIGS. 2A-2B illustrate anexemplary lateral approach to the spine. In typical lateral approaches,after making an incision in the psoas muscle 102, the surgeon places anumber of sequential circular dilators 104 _(1-n), each larger indiameter, on the desired pathway to the spine 100 through the psoasmuscle 102 to dilate the surgical site radially away from the initialincision site or K-wire insertion point. This dilation process can leadto compression of muscle, nerves, and blood supplies adjacent to thevertebral body, which can lead to ipsilateral upper thigh pain, hipflexor weakness that causes difficulty in walking and/or stair climbing,and muscle atrophy that follows from muscle injury.

After the series of circular dilators are forced into the muscle tissue,a multi-bladed or tubular retractor apparatus 106 may be placed over thefinal dilator 104 _(n). The retractor is then retracted radially toseparate the psoas muscle and other soft tissues. A common problemassociated with this type of lateral procedure is that soft tissues,including the musculature and nerves surrounding the spine, becomecrushed and/or trapped near the distal end of the retractor's bladeswhen the retractor is passed over the final dilator, a problem oftenreferred to as “trappage,” graphically depicted in FIG. 3.

In order for the surgeon to clear the surgical pathway to the discspace, or to “see” the disc space, the surgeon must cauterize and cutthe muscle that is caught inside the retractor, effectively performing amuscle biopsy each time the surgeon performs an XLIF, DLIF, OLIFprocedure. Beyond undesired muscular damage to the patient, thisapproach requires additional effort for the surgeon to utilize a cauteryor similar device to remove the trapped soft tissues from between thedistal end of the retractor and the vertebral bodies prior to completingaccess to the spine.

Oftentimes the resulting damage and trauma to the soft tissue resultingfrom trappage and removal of psoas muscle tissue with a cautery causeslasting problems for a patient. For instance, a patient who experiencestrappage during surgery will often have ipsilateral upper thigh pain andleg weakness. Such pain and leg weakness occurs due to the linkage ofthe psoas to the lower body, as the psoas muscle connects to the femur.Thus, damage to the psoas will generally manifest in lower bodydiscomfort, including pain and weakness in the leg.

Another problem associated with existing lateral surgical approaches tothe spine is nerve damage. The lumbar plexus is a web of nerves (anervous plexus) in the lumbar region of the body which forms part of thelarger lumbosacral plexus. The lumbar plexus in particular is oftendamaged as a direct result of surgical intervention utilizing thelateral approach to the spine. The nerves associated with the lumbarplexus can experience indirect nerve injury as a result of over-dilationor over-retraction of apparatuses utilized to accomplish lateral accessto the spine. They also can experience direct nerve injury as a resultof direct trauma caused by impingement from the instrumentation utilizedduring the surgical intervention in association with the lateralapproach to the spine, as in the case of trappage, discussed above. Suchindirect and direct nerve damage can cause numbness in part or all ofthe leg and can lead to indirect muscle atrophy. A recent meta-analysisreview of 24 published articles indicates that the lateral approach isassociated with up to a 60.7% complication rate. Gemmel, Isaac D, et.al, Systemic Review of Thigh Symptoms after Lateral Transpsoas InterbodyFusion for Adult Patients with Degenerative Lumbar Spine Disease,International Journal of Spine Surgery 9:62 (2015). The review furtherfound that the retractors resulted in 43% psoas muscle pain, 30.8% psoasmuscle weakness, and 23.9% nerve or plexus injury due to the inherentlyflawed design of existing commercially available retractors.

One existing method of neuromonitoring involves the insertion of anumber of epidural electrodes into the lumbar plexus. Stimulation of theelectrodes is used to trigger a response in the patient's nervestructures, and the resulting evoked potentials correspond to the neuralactivities of the nerve structures near the recording electrodes. Thepotentials may be recorded to detect reactions in the nervous systemthat may indicate a problem, including some type of impingement orencroachment of an instrument upon the nerve structures during aprocedure. This method, while providing information relating to a changein the behavior of the nerve structures nearby the inserted electrodes,does not directly correlate to a change in the behavior of the nervestructures in response to a nearby surgical instrument such as a dilatoror a retractor, and is therefore not optimal for identifying impingementfrom the instrumentation utilized during the surgical intervention.

In addition, existing dilators oftentimes incorporate a vertical wireconductor that extends through the outer wall of the dilator parallel tothe longitudinal axis of the apparatus, terminating in a pinpointelectrode at the distal end of the apparatus. The electrode maystimulate nearby nerve structures to asses for any impingement uponnerve or plexus. Because the vertical wire provides only a pinpointelectrode, the surgeon must manually rotate the apparatus through 360degrees to perform a full range of neuromonitoring for impingement uponall of the adjacent neurological structures surrounding the device: thefront and the back, superior and inferior. This additional step iscumbersome and presents challenges in achieving thoroughneuromonitoring. Moreover, because existing dilators with pinpointelectrodes require the surgeon to rotate the dilators to achieveneuromonitoring in 360 degrees, the dilators cannot perform a full rangeof monitoring once they are affixed. After fixation, only pinpointmonitoring is provided, and existing devices cannot provide continuous,real-time neuromonitoring throughout the procedure.

Existing retractor systems also present challenges in terms ofillumination and require a separate light source that attaches to thetop of the retractor. This separate device is cumbersome, physicallyinterfering and disruptive, and the limited ability to position thelight source oftentimes means that light reflects off of the retractorblades before returning to the surgeons eyes, which leads to suboptimalvisualization of the surgical area.

Existing retractor systems also lack ease of adjustability and are notdesigned with an eye toward ergonomic use by the surgeon, who is forcedto hunch over the retractor apparatus during the course of the procedureto direct the surgical equipment as desired.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key aspects oressential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

One embodiment provides a lateral retractor system for forming asurgical pathway to a patient's intervertebral disc space. The lateralretractor system may include: (1) a dilator having a narrow body definedby opposing flat surfaces that extend between a proximal end and adistal end, the distal end tapering to a distal edge configured forinsertion at an insertion orientation in which the opposing flatsurfaces are parallel to a plurality of psoas muscle fibers and angledrelative to the disc space; and (2) a retractable dual-blade assemblyconsisting of two opposing blade subassemblies, each of the bladesubassemblies comprising: (a) a blade having a planar inner surface, anouter surface, a proximal blade portion, a distal blade portion, andopposing longitudinal edges extending from a proximal end of theproximal blade portion to a distal end of the distal blade portion; and(b) an adjustable wing hingedly coupled with each of the opposinglongitudinal edges of the blade, the adjustable wing configured to movebetween an open position parallel to the planar inner surface of theblade and a closed position perpendicular to the planar inner surface ofthe blade, the retractable dual-blade assembly configured to pass overthe dilator at the insertion orientation such that the planar innersurfaces of the blades contact the opposing flat surfaces of thedilator.

Another embodiment provides a lateral retraction system for minimizingdamage to a patient's muscle fibers and nerve structures when forming asurgical pathway to the patient's spine. The lateral retraction systemmay include: (1) a dilator having a narrow body defined by opposing flatsurfaces that taper to a distal edge configured for insertion adjacentto an intervertebral disc space at an insertion orientation in which theopposing flat surfaces of the dilator are parallel to a plurality ofpsoas muscle fibers and at an approximate 45 degree angle to thepatient's spine; and (2) a lateral retractor, including (a) a dual-bladeassembly consisting of a pair of blade subassemblies, each having ablade with a planar inner surface and an outer surface, the dual-bladeassembly configured to pass proximally-to-distally over the dilator atthe insertion orientation such that the planar inner surface of theblade of each of the blade subassemblies contacts one of the opposingflat surfaces of the dilator; (b) a rotation assembly operably coupledbetween the dual-blade assembly and a surgical table, the rotationassembly configured to rotate the dual-blade assembly about alongitudinal center axis of the dilator from the insertion orientationto a rotated orientation in which the planar inner surface of each ofthe blades is parallel to the intervertebral disc space; and (c) alateral retraction assembly operably coupled between the dual-bladeassembly and the surgical table, the lateral retraction assemblyconfigured to separate the pair of the blade subassemblies from oneanother.

Yet another embodiment provides a dilation system for use with a lateralretraction assembly for forming a surgical pathway to a patient'sintervertebral disc space. The dilation system may consist of a singledilator having a narrow body defined by opposing first and second flatsurfaces that extend proximally-to-distally from a proximal end to adistal end, wherein the distal end of the body tapers to a distal edgealong a first tapered surface and an opposing second tapered surface,the distal edge of the dilator configured for insertion at an insertionorientation in which the first and the second flat surfaces are disposedat approximately a 45-degree angle to the patient's disc space andparallel with a plurality of psoas muscle fibers of the patient.

Another embodiment provides a method of forming a surgical pathwaythrough a side of a patient's body and through a psoas muscle to anintervertebral disc space. The method may include the following steps:(1) providing a dilator having a narrow body defined by opposing flatsurfaces that extend from a proximal end to a distal end, the distal endtapering to a distal edge; (2) positioning the dilator at an insertionorientation in which the opposing flat surfaces of the dilator aredisposed parallel to the psoas muscle; (3) using the distal edge of thedilator, traversing a plurality of fibers of the psoas muscle until thedilator spans the intervertebral disc space at the insertion orientationin which the opposing flat surfaces of the dilator are disposed parallelto the plurality of the fibers of the psoas muscle and at an angle ofapproximately 45 degrees to the intervertebral disc space; and (4) via ak-wire extending longitudinally through a center of the dilator,securing the dilator within the intervertebral disc space at theinsertion orientation.

A further embodiment provides a method of creating a surgical pathway toa patient's spine using a lateral retractor system including a singleplanar dilator having a flat cross-section that tapers to a distal edge,a retractable blade assembly including two opposing blades that eachtaper to a distal edge, a rotation assembly operably coupled with theretractable blade assembly, and a retraction assembly operably coupledwith the retractable blade assembly. The method may include thefollowing steps: (1) inserting the single planar dilator through a psoasmuscle of the patient such that the distal edge of the single planardilator spans an intervertebral disc space at an insertion orientationthat is parallel to a plurality of fibers of the psoas muscle; (2) usinga k-wire extending longitudinally through a center of the single planardilator, anchoring the single planar dilator at the intervertebral discspace; (3) rotating the single planar dilator about the k-wire from theinsertion orientation that is parallel to the psoas muscle to a rotatedorientation that is parallel to the intervertebral disc space; and (4)during the steps of inserting, anchoring, and rotating the single planardilator, and using a first active neuromonitoring tip positionedadjacent to the distal edge of the single planar dilator, monitoring foran encroachment upon one or more nerve structures of the patient locatedadjacent to any portion of a circumference of the first activeneuromonitoring tip.

Yet another embodiment provides a method of forming a surgical pathwayto a patient's spine. The method may include the following steps: (1)providing a dilator having a body with a flat cross-section defined bytwo opposing flat surfaces that taper to a distal edge via two opposingtapered surfaces; (2) positioning the dilator over an intervertebraldisc space of the patient at an insertion orientation in which the twoopposing flat surfaces are parallel to one or more fibers of a psoasmuscle of the patient; (3) passing a k-wire longitudinally through acenter of the dilator; (4) securing the k-wire at the intervertebraldisc space; (5) passing a dual-blade assembly proximally-to-distallyover the dilator, the dual-blade assembly having (a) two opposingblades, each having a planar inner surface and an outer surface thatextend from a proximal end of a reusable proximal portion to a distalend of a disposable distal portion along two longitudinal edges; and (b)an adjustable wing hingedly coupled with each of the two longitudinaledges of each of the two opposing blades; (6) operably coupling arotation assembly to the dual-blade assembly; (7) using the rotationassembly, rotating the dual-blade assembly and the dilator about thek-wire from the insertion orientation to a rotated orientation in whichthe two opposing flat surfaces of the dilator are parallel to theintervertebral disc space; (8) operably coupling a lateral retractionassembly to the dual-blade assembly; and (9) using the lateralretraction assembly, separating the two opposing blades of thedual-blade assembly from one another.

A further embodiment provides a retractable blade assembly for use informing a surgical pathway to an intervertebral disc space of apatient's spine. The retractable blade assembly consists of: (1) a firstblade subassembly detachably attached to a second opposing bladesubassembly, each of the first and the second blade subassembliescomprising (a) a blade defined by a planar inner surface, an outersurface, and two longitudinal edges, the blade including a proximalblade portion extending from a proximal end to a distal end that isattached to a distal blade portion extending from a proximal end to adistal edge.

Still another embodiment provides a dual-blade assembly for placementabout a narrow planar dilator in forming a surgical pathway to apatient's spine, the dual-blade assembly comprising not more than tworetractable blades, the retractable blades opposing one another andconfigured to separate from one another, each of the retractable bladescomprising an opposing inner surface having a planar geometry.

An additional embodiment provides a dual-blade assembly for forming asurgical pathway to a patient's spine. The dual-blade assembly mayinclude: (1) a first blade subassembly having (a) a first blade definedby a first outer surface, a first planar inner surface, and two firstlongitudinal sides; and (b) a first opposing adjustable wing hingedlycoupled with each of the first longitudinal sides; (2) a second bladesubassembly having (a) a second blade defined by a second outer surface,a second planar inner surface, and two second longitudinal sides; and(b) a second opposing adjustable wing hingedly coupled with each of thesecond longitudinal sides; and (3) a coupling device configured todetachably attach the first and the second blade subassemblies such thatthe first and the second planar inner surfaces oppose one another,wherein the dual-blade assembly is configured to provide threemodalities of motion including: (i) when the coupling device is anattached configuration, rotation of the dual-blade assembly about acenter longitudinal co-axis of the first and the second blades; (ii)when the coupling device is in a detached configuration, retraction ofthe first and the second blade subassemblies from one another; and (iii)when the coupling device is in the detached configuration, rotation ofthe first and the second opposing adjustable wings relative to the firstand the second planar inner surfaces of the first and the second blades,respectively.

Still another embodiment provides a lateral retractor system for forminga surgical pathway through a plurality of psoas muscle fibers to apatient's intervertebral disc space, comprising a dilator including: (1)a conductive body defined by opposing flat surfaces that extend betweena proximal end and a distal end; (2) a first nonconductive layerdisposed upon an outer surface of the conductive body; (3) a firstactive neuromonitoring tip protruding from the distal end of theconductive body to a leading distal edge configured for insertion intothe intervertebral disc space; and (4) a first conductive electricalpathway extending from a first conductive input surface at the proximalend of the conductive body, through the conductive body, and to thefirst active neuromonitoring tip such that an electrical signal appliedto the first conductive input surface causes the first activeneuromonitoring tip to simultaneously and continuously stimulate one ormore nerve structures located adjacent to any portion of a circumferenceof the distal end of the conductive body to assess for an encroachmentof the dilator upon the one or more of the nerve structures.

Yet another embodiment provides a dilation system for minimizing damageto a patient's psoas muscle fibers when forming a surgical pathway to anintervertebral disc space of the patient's spine. The dilation systemmay include a dilator having: (1) a conductive body portion comprisingtwo opposing flat surfaces that extend between a proximal end and distalend; (2) an insulative coating overlaying the conductive body portion;and (3) a conductive neuromonitoring portion extending distally from thedistal end of the conductive body portion to a leading distal edgeconfigured for insertion between the patient's psoas muscle fibers,wherein when an electrical dilator stimulus is applied to the proximalend of the conductive body portion, the electrical dilator stimuluspropagates through the conductive body portion to the conductiveneuromonitoring portion such that the conductive neuromonitoring portionsimultaneously stimulates one or more nerve structures located adjacentto any point about a circumference of the conductive neuromonitoringportion.

Another embodiment provides a retraction system for forming a surgicalpathway through a patient's psoas muscle to the patient's intervertebraldisc space, comprising: (1) a planar dilator for traversing a pluralityof fibers of the patient's psoas muscle, the planar dilator having adilator body portion with opposing flat surfaces and a dilatorneuromonitoring portion extending distally from the dilator bodyportion; (2) a dual-blade retractor having opposing retractable blades,each of the opposing retractable blades configured to pass over theplaner dilator such that each of the opposing retractable bladescontacts one of the opposing flat surfaces of the planar dilator, eachof the opposing retractable blades having a blade body portion and ablade neuromonitoring portion extending distally from the blade bodyportion, wherein: (a) the planar dilator and each of the opposingretractable blades are conductive such that an electrical dilatorstimulus applied to the dilator body portion propagates to the dilatorneuromonitoring portion and an electrical blade stimulus applied to theblade body portion of each of the opposing retractable blades propagatesto each of the blade neuromonitoring portions to simultaneously andcontinuously stimulate one or more nerve structures located adjacent toany portion of a circumference of the dilator neuromonitoring portionand any portion of a circumference of each of the blade neuromonitoringportions to assess for an encroachment of the planar dilator and thedual-blade retractor upon the one or more of the nerve structures.

Other embodiments are also disclosed.

Additional objects, advantages and novel features of the technology willbe set forth in part in the description which follows, and in part willbecome more apparent to those skilled in the art upon examination of thefollowing, or may be learned from practice of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention,including the preferred embodiment, are described with reference to thefollowing figures, wherein like reference numerals refer to like partsthroughout the various views unless otherwise specified. Illustrativeembodiments of the invention are illustrated in the drawings, in which:

FIGS. 1A-1B illustrate perspective and top partial views, respectively,of a patient's spine comprised of sequential vertebrae, each separatedby an intervertebral disc space, with an attached psoas muscle group;

FIGS. 2A-2B illustrate perspective views of a prior art retractionsystem including a series of increasing-diameter dilators and a circularlateral retractor, as inserted into the spine of FIGS. 1A-1B;

FIG. 3 illustrates a bottom-plan view of the prior art dilators andlateral retractor of FIGS. 2A-2B, as inserted into the psoas muscle andtrapping the muscle fibers;

FIGS. 4-6 illustrate respective perspective, top, and front views of oneembodiment of a rectangular dilator, as inserted at an insertionorientation through a patient's side body and through the psoas muscleover the intervertebral disc space of FIGS. 1A-1B;

FIG. 7 illustrates a perspective view of the rectangular dilator ofFIGS. 4-6;

FIG. 8 illustrates a perspective view of the rectangular dilator ofFIGS. 4-6, as inserted at the insertion orientation through the psoasmuscle over the intervertebral disc space and having a monitor cablecoupled with a conducting wire in electronic communication aneuromonitoring tip of the dilator;

FIGS. 9-10 illustrate perspective and side views, respectively, of oneembodiment of a dual-blade assembly passed over the inserted dilator ofFIGS. 4-8 in the insertion orientation;

FIGS. 11-14 illustrate left-perspective, right-perspective, top-plan,and left-bottom-perspective views, respectively, of one embodiment of ablade subassembly of the dual-blade assembly of FIGS. 9-10;

FIG. 15 illustrates a perspective view of the dual-blade assembly ofFIGS. 9-10 installed in the insertion orientation, without a lowercoupling device and disposed upon a surgical table in preparation forconnection with a lateral retraction gearbox;

FIG. 16 illustrates a perspective view of the dual-blade assembly ofFIGS. 9-10 including a lower coupling device attaching two of the bladesubassemblies of FIGS. 11-14, in preparation for connection with thelateral retraction gearbox of FIG. 15;

FIG. 17 illustrates a perspective view of the dual-blade assembly ofFIG. 16 in the insertion orientation, connected to the lateralretraction gearbox of FIGS. 15-16 via one embodiment of a rotationassembly;

FIG. 18 illustrates a perspective view of the connected dual-bladeassembly, lateral retraction gearbox, and rotation assembly of FIG. 17,with the dual-blade assembly rotated to a final rotated orientation viathe rotation assembly;

FIG. 19 illustrates a perspective view of one embodiment of a rotationgearbox and connecting rods of the rotation assembly of FIGS. 17-18;

FIG. 20 illustrates a perspective view of the connected dual-bladeassembly, lateral retraction gearbox, and rotation assembly of FIGS.17-18, with a handle of the rotation assembly removed and an embodimentof a pair of opposing passive lateral arms coupled between thedual-blade assembly and the lateral retraction gearbox;

FIG. 21 illustrates the assembly of FIG. 20, with a gearbox of therotation assembly removed;

FIG. 22 illustrates a perspective view of the assembly of FIG. 21, withone embodiment of a pair of opposing lateral drive arms coupled betweenthe dual-blade assembly and the lateral retraction gearbox;

FIG. 23 illustrates a perspective view of the assembly of FIG. 22, witha K-wire and a lower coupling device removed from the dual-bladeassembly to an exploded position;

FIG. 24 illustrates a perspective view of the assembly of FIG. 23, withthe dilator of FIGS. 4-8 removed to an exploded position;

FIG. 25 illustrates a perspective view of the assembly of FIG. 24, witha housing of the lateral actuation gearbox removed to reveal oneembodiment of a lateral retraction gear chain operating within thehousing;

FIGS. 26-27 illustrate top views of two adjacent blade subassemblies ofFIGS. 11-14 coupled with one embodiment of a lateral retraction assemblyand in a closed blade position;

FIG. 28-30 illustrate top views of the two blade subassemblies coupledwith the lateral retraction assembly of FIGS. 26-27 in a retracted bladeposition;

FIG. 31 illustrates a perspective view of the two blade subassembliescoupled with the lateral retraction assembly in the retracted bladeposition of FIG. 30, as inserted through the patient's side body;

FIG. 32 illustrates a perspective view of one embodiment of a fullyassembled lateral retraction system;

FIG. 33 illustrates a perspective view of a surgical area illuminatedusing LEDs built into one embodiment of the lateral retraction system ofFIG. 32;

FIG. 34 illustrates a perspective view of an image area covered by avideo camera incorporated within one embodiment of the lateralretraction system of FIG. 32;

FIGS. 35A-35B provide a flowchart depicting an exemplary method ofcreating a surgical pathway to the patient's spine using the assembliesand systems of FIGS. 4-34

FIGS. 36A-36B illustrate perspective and cross-sectional views ofanother embodiment of a planar dilator featuring non-wired, continuous,and simultaneous neuromonitoring about 360-degrees of a circumference ofthe dilator; and

FIGS. 37A-37F illustrate respective front, rear,partial-rear-perspective, partial-side-perspective, unassembledpartial-rear perspective, and assembled partial-rear perspective viewsof one embodiment of a blade and adjustable wings for incorporation intothe blade subassembly of FIGS. 11-18, featuring non-wired, continuous,and simultaneous neuromonitoring about 360-degrees of a circumference ofthe blade and the adjustable wings.

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail toenable those skilled in the art to practice the system and method.However, embodiments may be implemented in many different forms andshould not be construed as being limited to the embodiments set forthherein. The following detailed description is, therefore, not to betaken in a limiting sense.

This disclosure details a system and method of use for a lateralapproach to creating a minimally invasive surgical pathway through apatient's side body and psoas muscle 102 to the intervertebral discspace 110 of the spine 100. Embodiments may include a lateral retractorsystem having a flat, narrow dilator having a body that tapers to adistal edge. The dilator inserted in a diagonal orientation that isparallel to the angled fibers of the psoas muscle and anchored into thedisc space 110 via a K-wire. The dilator may be used in conjunction witha dual-blade lateral retractor that may be placed in a correspondingdiagonal orientation over the flat, narrow dilator before the entiresystem is rotated approximately 45-50 degrees to the horizontal, oruntil the dilator and the lateral retractor are parallel with the discspace 110, as shown and discussed in FIGS. 17-18 below. Once the systemis rotated, the dilator may be removed and the dual blades of thelateral retractor may be laterally separated to push the muscle fibersaway and to complete the surgical pathway in a manner that minimizesentrapment of, impingement upon, and/or damage to the patient's musclefibers and nerve structures. Because the dilator is narrow or flat inshape, which allows the dilator to be placed in its insertionorientation parallel to the muscle fibers and then rotated to its finalrotated orientation parallel to the disc space, the system functionswith a single element or component dilator, rather than requiringplacement of a series of sequentially larger circular dilators, asdiscussed in the Background section above.

Both the dilator and the lateral retractor may incorporate real-time,360 degree neuromonitoring through stimulated horizontal wiringpositioned on the external sides/surfaces of each of the distal dilatortip and the distal ends of the blades of the lateral retractor, enablingreal-time and continuous neuromonitoring throughout the procedure fromfront to back and superior to inferior. Embodiments of the lateralretractor system may also incorporate built-in LED lighting for superiorsurgical visualization, as well as micro-video capabilities that enablethe system to be operated in the most ergonomic and efficient fashion.

Turning to exemplary embodiments, FIGS. 4-34 and 35A-35B generallyillustrate a method of using embodiments of a disclosed lateralretractor system 200 (FIG. 32) to employ a lateral surgical approach toclear a surgical pathway 114 to a patient's spinal disc space 110.Specifically and in one embodiment, FIGS. 4-34 detail a number of stepsin which exemplary devices are in use to create the surgical pathway 114through the side of a patient's body 108, through the psoas muscle 102,and to the intervertebral disc space 110, while FIGS. 35A-35B provide aflowchart depicting an exemplary method 500 of creating the surgicalpathway 114 through the side of the patient's body 108 through the psoasmuscle 102 to the disc space 110.

Employing fluoroscopy imaging technology, a dilator 202 may be placedover/adjacent to the intervertebral disc space 110 (FIG. 35A, 501).Specifically, and referring to FIGS. 4-7, the dilator 202 may enterthrough an incision 118 in the patient's side body 108 (FIG. 35A, 502),cut through any intervening fascia (FIG. 35A, 504), and then traversethe psoas muscle 102 in a direction, or at an insertion orientation 239,that is “along,” or parallel to the muscle fibers of the psoas muscle102, and diagonal to, or angled at approximately 45 degrees to, thepatient's spine 100 (FIG. 35A, 506). The psoas muscle 102 may beaccessed via the side of the patient's body 108 such that the dilator202 protrudes from a lateral surface 116 of the patient's body 108 wheninserted to full depth at the spinal column 100.

FIG. 7 illustrates a perspective view of one embodiment of the dilator202. In this embodiment, the dilator 202 may feature a flat, narrow body204 having opposing flat surfaces 209 that extend between a proximal end206 for positioning at the lateral surface 116 of the patient's sidebody 108 (FIG. 4) and a distal end 208 for positioning adjacent thepatient's spine 100. The longitudinal sides of the narrow body 204 ofthe dilator 202 may taper to opposing longitudinal edges 212, and thedistal end 208 of the dilator 202 may taper to a distal edge 210 capableof cutting through the patient's fascia and traversing the fibers of thepsoas muscle 102 in the parallel manner described above. As a result,the dilator 202 separates, rather than crushes, the fibers of the psoasmuscle 102 as it traverses through the psoas muscle 102 to the spine100, as shown in FIGS. 4-6 and 8.

The dilator 202 may also include a K-wire access aperture 216 thatextends longitudinally through the body 204 of the dilator 202. Inaddition, conducting wires 218 may extend longitudinally through eachside of the body 204 of the dilator 202. At the distal end 208 of thedilator 202, the conducting wires 218 may be in electronic communicationwith a set of horizontal neurosensing wires 220 that are integrated orbuilt into each side of the tapered distal end 208 of the dilator 202.At the proximal end 206 of the dilator, the conducting wires 218 may bein electronic communication with a monitoring cable 224, shown in FIG.8, which may be configured to conduct an electronic stimulus through theconducting wires 218 to the horizontal neurosensing wires 220, formingan active neuromonitoring tip 222 about an entirety of the distal end208 of the dilator 202.

Impingement of the active monitoring tip 222 upon, or alternatively,encroachment of the active monitoring tip 222 in close proximity tonerve structures located along the patient's spine 100 may stimulatethose nerve structures that are nearby or adjacent to the activemonitoring tip 222. The voltage of the applied electronic stimulus maybe adjusted as necessary and/or required to stimulate nerve structureswithin a defined distance of the active monitoring tip 222. This appliedstimulus causes the nerve structure(s) to fire and generate a responsivesignal, which may in turn be conducted from the active monitoring tip222, through the conducting wires 218, and to the monitoring cable(s)224 in electronic communication with one or both of the conducting wires218 at the proximal end 206 of the dilator 202, as shown in FIG. 8,thereby translating the neurosensing stimulation of the activemonitoring tip 222 by the nearby nerve structure(s) to externalmonitoring equipment (not shown) via the monitoring cable 224 anddetermining, in real time and with 360 degrees of monitoring range orfield of view about the distal end 208 of the dilator 202, a possibilityof nerve or plexus injury as the dilator 202 is inserted (FIG. 35A,508).

Embodiments of the dilator 202 and its components may be formed of anyappropriate conductive or nonconductive, autoclavable or otherwisesterilizable metal or plastic. In addition, the body 204 of the dilator202 may have any appropriate length to accommodate the patient's size,shape, and/or physiology. In one embodiment, the dilator 202 may beprovided in a variety of lengths, allowing the surgeon to select inreal-time the appropriate length for the patient.

Once the distal edge 210 of the dilator 202 is positioned at the spine100 in the insertion orientation 239 that is parallel to the fibers ofthe psoas muscle 102 and spanning the disc space 110 diagonally at anapproximate 45-degree angle, a K-wire 214 may be passed longitudinallythrough the access aperture 216 of the dilator 202 and into the spine100 at the disc space 110 (FIG. 35A, 510), both stabilizing and securingthe position of the dilator 202, as shown in FIGS. 6 and 8. Because ofthe active monitoring tip 222, the full range of monitoring—front toback and superior to inferior—may continue after the dilator 202 isfixed via the k-wire 214. Unlike previous devices featuring pinpointelectrodes that require manual rotation to perform 360 degrees ofmonitoring, the active monitoring tip 222 remains active and provides ageometry capable of monitoring in 360 degrees during every stage of itsinsertion and use during a procedure.

Referring to FIGS. 9-10, after securing the K-wire 214 (FIG. 35A, 510)into the disc space 110 of the spine 100 such that the dilator 202 isstabilized, secured, and providing continuous neuromonitoring, adual-blade assembly 230 of a dual-blade lateral retractor system 200(FIG. 32) may be passed over or introduced at the insertion orientation239 alongside the dilator 202 such that each blade 244 of the dual-bladeassembly 230 opposes and contacts one of the opposing flat surfaces 209of the dilator 202 to further minimize damage to nerve structures andmuscle fibers (FIG. 35A, 512).

As shown in FIGS. 9-10, the dual-blade assembly 230 may include twoopposing and identical blade subassemblies 240 coupled to one anothervia a lower coupling device 242 configured to snap or press fit intoreceiving structures formed within each of the blade subassemblies 240.The lower coupling device 242 may include a platform 241 having aplurality of protrusions extending from a bottom of the platform 241that are sized to be received by each of the blade subassemblies 240.The protrusions may include two opposing rectangular protrusions 243 andfour opposing circular protrusions 245, each for insertion into acorresponding one of the blade subassemblies 240. The lower couplingdevice 242 may also include two circular receivers 247 formed within atop of the platform 241 and configured to receive components ofadditional functional assemblies that stack above the blade assembly230, as detailed further below.

FIGS. 11-13 illustrate front-perspective, rear-perspective, and top-planviews of one exemplary embodiment of the blade subassembly 240,respectively. In this embodiment, the blade subassembly 240 may includea blade 244 having a planar inner surface 235 that faces the opposingblade 244 of the dual-blade assembly 230 (FIGS. 9-10), an outer surface237, a proximal blade portion 246, a detachable distal blade portion248, and opposing longitudinal edges 250 that extend between a proximalend 260 of the proximal blade portion 246 and a distal end 255 of thedistal blade portion 248. Opposing adjustable wings 252 may be hingedlycoupled with each of the opposing longitudinal edges 250, as detailedfurther below.

Turning to the blade 244, the detachable distal portion 248 may be adisposable, single-use insert of any appropriate length to accommodatethe patient's size or physiology. In one embodiment, a plurality ofdetachable distal portions 248 may be provided in a peel pack (notshown), where each of the distal portions 248 contained within the peelpack feature a different length to accommodate a variety patient sizesand/or physiologies, which results in a variety of distances to traversebetween the lateral surface 118 of the patient's body 108 and the spine100. During use, the surgeon may select the detachable distal bladeportion 248 with the appropriate length before attaching the selectdistal blade portion 248 to the reusable and sterilizable proximalportion 246 of the blade 244. The detachable distal portion 248 mayattach to the reusable proximal portion 246 in any appropriate mannerincluding, for example, a snap-fit of mating components or, as shown inFIG. 12, via an attachment screw 254 or another appropriate threadedfastener.

In one embodiment, the distal end 255 of the distal portion 248 of theblade 244 may form an active monitoring tip 256 similar to the activemonitoring tip 222 of the dilator 202. In this regard, horizontalneurosensing wires 258 may be incorporated or built into the outersurface 237 of the blade 244 at the active monitoring tip 256. Thehorizontal neurosensing wires 258 may detect any impingement orencroachment upon nerve or plexus, and the resulting stimulus may beconducted through conducting wires embedded longitudinally in the blade,and through a monitoring cable for reporting to external equipment. Viathe active monitoring tip 256 of each of the distal blade portions 248of the blades 244, continuous real-time neuromonitoring may be performedto prevent nerve or plexus injury when the blade assembly 230 isinserted over the dilator 202 (FIG. 35A, 512, 514), as well as when theblade assembly 230 is rotated (FIG. 35A, 516) and/or laterally separatedor retracted (FIG. 35A, 524), as discussed below. Unlike existingsystems, neuromonitoring over a full 360-degree monitoring range maycontinue throughout the procedure.

The sterilizable and reusable proximal blade portion 246 may include anumber of unique features that aid the surgeon. In one embodiment, theproximal end 260 of the proximal blade portion 246 may form a generallyrectangular receiver 262 configured to receive one of the rectangularprotrusions 243 of the lower coupling device 242 (FIGS. 9-10), which isadapted to temporarily couple the dual, opposing blade subassemblies 240to one another during insertion and assist in rotating the bladesubassemblies 240 from the insertion orientation 239 to a final, rotatedorientation, as discussed below in relation to FIGS. 17-18.

In addition, and referring to FIGS. 11-14, one or more light emittingdiode (LED) lights 264 may be built into the proximal blade portion 246.As shown in FIGS. 11 and 14 and in this embodiment, three LED lights 264may be positioned adjacent to the inner surface 235 of a distal end 261of the proximal blade portion 246, such that the LED lights 264illuminate a surgical area 266, as shown in FIG. 11. In one embodimentshown in FIG. 14, the LED lights 264 may be mounted to a printed circuitboard (PCB) 265 housed within a PCB chamber 267 formed within theproximal blade portion 246 of the blade 244. The PCB 265 may incorporatecontrol or interface circuitry that is, in turn, electrically coupledwith a power source and a switch 272. In this embodiment, the powersource may be one or more lithium ion batteries 268 housed within abattery housing 270 that is affixed in any appropriate manner to theouter surface 237 of the blade 244, as shown in FIGS. 11-13. The switch272 may be electrically coupled between the batteries 268 and the PCB265/LED lights 264, such that the switch 272 is configurable to controlthe lights 264 as necessary and/or desired by the surgeon. For example,the switch may be operated to illuminate a single one of the LED lights264, a pair of the lights 264, or all of the LED lights 264 depending onthe applicable light requirements and/or requisite run times.

Built-in lighting on the inner surfaces 235 of the blades 244 providesmore accurate visualization for the surgeon due to the proximity of thelight emitting source to the surgical field 266. The built-in lightingalso eliminates the need for an external extension cord for lightingpurposes, and prevents light projected from a separately attached lightsource, which is often attached to a proximal end of the apparatus, fromreflecting off the blades and into the surgeon's eyes during operation.

The blade 244 may also include video capability to provide ergonomicoperation for the surgeon. Specifically, and in one embodiment shown inFIG. 14, an interior of the proximal blade portion 246 may form a camerareceiver channel 274 into which a video camera 276 (e.g., a commerciallyavailable micro-video camera) may be fed or positioned to provide aclear view of the surgical field 266. Images captured by the videocamera 276 may be transmitted to one or more external monitors (e.g.,flat screen television monitors) (not shown) via a video output 278electronically coupled between the video camera 276 and the monitor(s).In one embodiment, the video camera 276/video output 278 may employwireless technology such as, for example, a Bluetooth, Zigbee, Wi-Fi oranother appropriate transmitter or transceiver to communicate with theexternal monitoring devices. This video capability enables the surgeonto view his or her work within the surgical field 266 inside thedual-blade assembly 230 on the external monitors, and relieves thesurgeon of the need to look straight down the assembly throughout thecourse of the procedure being performed.

As discussed above, each of the longitudinal edges 250 of the blade 244may hingedly couple with an adjustable wing 252, as shown in FIGS.11-14. As detailed below in relation to FIGS. 25-31, the adjustablewings 252 may be rotated or adjusted through 90 degrees relative to theinner surface 235 of the blade 244—from an open position 280 that isparallel with the blade 244 (FIGS. 25-27) to a closed position 282 thatis perpendicular to the blade 244 (FIG. 30), and any positiontherebetween (FIGS. 28-29). This adjustment from the open position 280to the closed position 282 essentially sections off the musclesurrounding the dual-blade assembly 230 as the blades 244 are separatedor retracted away from one another, thereby preventing any “creep” ofthe muscle between the blades during retraction and enabling thedual-blade assembly 230 to accomplish what has previously requiredadditional blades (e.g., multiple blades beyond two, a circular orradial blade configuration) to complete.

FIGS. 12-13 illustrate a perspective view of the blade subassembly 240and a top view of the blade subassembly 240 with the battery housing 270removed, respectively. Specifically, FIGS. 12-13 detail an exemplaryactuation assembly 290 for the adjustable wings 252 on each blade 244.In this embodiment, the actuation assembly 290 may include a centralmiter gear 292 positioned horizontally such that a center axis 294defined by the central miter gear 292 runs parallel to the blade 244. Atop of the central miter gear 292 may form a hexagonal socket 296configured to receive an actuating hex key (not shown), which may takethe form of a removeable manual handle such as handles 310 and 316,discussed below in relation to the rotation and lateral retractionassemblies.

The central miter gear 292 may be enmeshed between two opposing verticalmiter gears 298, each defining a center axis 300 that is perpendicularto and that intersects the center axis 294 of the central miter gear292. Each of the vertical miter gears 298 may be affixed to a worm screw302 that is, in turn, enmeshed with a corresponding worm wheel 304affixed to a proximal end of the associated adjustable wing 252. Tooperate, the hex key/handle may be rotated within the hexagonal socket296 to rotate the central miter gear 292, which, in turn rotates thevertical miter gears 298, the attached worms screws 302, and thecorresponding worm wheels 304 affixed each adjustable wing 252 to movethe wings 252 through 90 degrees in the direction of arrow C relative tothe inner surface 235 of the blade 244, as shown in FIGS. 25-31.

Like the lower blade portion 248, the adjustable wings 252 may besingle-use components that vary in length based upon an overall lengthof the blade 244 required to accommodate the patient's size and/orshape. Moreover, each of the adjustable wings 252 may form an activemonitoring tip 283 (FIG. 12) on its outer surface similar to the activemonitoring tips 222 and 256 of the dilator 202 and the blade 244,respectively.

Returning to the method and in relation to FIGS. 15-19, after thedual-blade assembly 230 is passed over the dilator 202 in a directionalong the fibers of the psoas muscle 102 (FIG. 35A, 512), the dual-bladeassembly 230 may be rotated approximately 45-50 degrees in the directionof arrow A about the K-wire 214, from its initial insertion orientation239 parallel to the fibers of the psoas muscle 102, shown in FIGS.15-17, to a final rotated orientation 306 parallel to the disc space110, in which the blades 244 of the dual-blade assembly 230 arepositioned transverse to the fibers of the psoas muscle 102 and begin toseparate the fibers of the psoas muscle 102, as shown in FIG. 18 (FIG.35B, 516).

To rotate the dual-blade assembly 230 from the insertion orientation 239to the rotated orientation 306 (FIG. 35B, 516), additional assembliesmay be operably coupled with the dual-blade assembly 230, as shown inFIGS. 15-19. Initially, a lateral actuation gearbox 308 and an actuatinghandle 310 may be securely attached to a fixed reference point such as asurgical table 233 via a standard tooth jaw and universal jointmechanism (not shown) (FIG. 35B, 518), as shown in FIG. 15. Then arotation assembly 312 may be coupled between the blade assembly 230 andthe lateral actuation gearbox 308 (FIG. 35B, 520).

In further detail and in one embodiment shown in FIGS. 17-19, therotation assembly 312 may include a rotation gearbox 314, an actuatinghandle 316, and a pair of connecting rods 318 coupled between therotation gearbox 314 and the lateral actuation gearbox 308, each havinga first end 320 affixed to the a housing 324 of the rotational gearbox314 and a second end 322 affixed to a housing 342 of the lateralactuation gearbox 308. The first and second ends 320, 322 of theconnecting rods 318 may be affixed to the rotational gearbox housing 324and the lateral actuation gearbox housing 342, respectively, in anyappropriate manner including, for example, via threaded fasteners.

FIG. 19 illustrates a perspective view of one embodiment of the rotationgearbox 314 and the connecting rods 318, with the housing 324 of therotation gearbox 314 in which the housing 324 is shown in wireframe toreveal the details of the gearbox 314. In this embodiment, the rotationgearbox 314 may contain first, second, and third rotational gears 326,328, 330, respectively, that are rotationally mounted relative to oneanother within the housing 324. The first rotational gear 326 mayinclude a hexagonal or other appropriately configured socket 332 adaptedto receive a distal end of the handle 316, which, in this embodiment,may be configured as a hex key. The third rotational gear 330 may beaffixed to an upper coupling device 334 having a top surface 336 adaptedto attach to the third rotational gear 330 and a bottom surface 338having two circular protrusions 340 extending therefrom. Each of thecircular protrusions 340 may, when the rotation gearbox 314 is assembledto the blade assembly 230 as shown in FIGS. 17-18, extend into thecircular receivers 247 of the lower coupling device 242 of the bladeassembly 230, shown in FIG. 16 and detailed above in relation to FIGS.9-10.

Once the rotation assembly 312 is coupled between the blade assembly 230and the lateral actuation gearbox 308 (FIG. 35B, 520), as shown in FIG.17, the handle may be manually actuated (FIG. 35B, 522) to turn thefirst rotational gear 326, which, in turn, rotates the enmeshed secondrotational gear 328 and then the enmeshed third rotational gear 330.Because the lateral actuation gearbox 308, the connecting rods 318, andthe rotation gearbox 314 are fixed relative to the operating table (notshown), rotation of the third rotational gear 330 causes the uppercoupling device 334 to turn the attached lower coupling device 242 aboutthe K-wire 214, which causes the two attached blade subassemblies 240 torotate in the direction of arrow A (FIGS. 15-16) from the initialinsertion orientation 239 of FIG. 17 to the final rotated orientation306 of FIG. 18.

After the dual-blade assembly 230 has been rotated into the finalrotated orientation 306 (FIG. 35B, 516), the system may be reconfiguredfor separation, or lateral retraction, of the two opposing bladesubassemblies 240 via the steps illustrated in FIGS. 20-25 (FIG. 35B,524). First, and as shown in FIG. 20, a pair of opposing passive lateralarms 344 may be attached between the lateral actuation gearbox 308 andthe battery housings 270 of the blade subassemblies 240 (FIG. 35B, 526).Each of the passive lateral arms 344 may have a first end 346 that isrotationally coupled with one of the battery housings 270 and a secondend 348 that is rotationally coupled with the housing 342 of the lateralactuation gearbox 308, such that the passive lateral arms 344 mayprovide stabilization to the blade assembly 230 as the rotation gearbox314 is removed, as shown in FIG. 21, as well as passively accommodatethe lateral separation of the blade subassemblies 240, as discussedfurther below in relation to FIGS. 26-31. The rotational couplingsbetween the passive lateral arms 344, the battery housings 270, and thelateral actuation gearbox 308 may take any appropriate shape,configuration, or type. In this embodiment, the first and the secondends 346, 348 of each of the passive lateral arms 344 may form areceiver 350 configured to receive a corresponding protrusion 352extending from the battery housing 270 and from the lateral actuationgearbox 308 via a friction fit.

Once the passive lateral arms 344 are attached (FIG. 35B, 526), therotation assembly 312, including the rotation gearbox 314, the manualhandle 316, and the connecting rods 318, may be removed as shown inFIGS. 20-21 by disengaging the upper and the lower coupling devices 334and 242, all the while relying on the passive lateral arms 344 forstabilization of the blade assembly 230 during removal (FIG. 35B, 528).Then a pair of opposing lateral drive arms 354 may be coupled betweenthe lateral actuation gearbox 308 and the battery housings 270 of theblade subassemblies 240 (FIG. 35B, 530), as shown in FIG. 22. Each ofthe lateral drive arms 354 may have a first end 356 that is rotationallycoupled to one of the battery housings 270 of the blade subassemblies240 and a second end 358 that is rotationally coupled to the housing 342of the lateral actuation gearbox 308. These rotational couplings maytake any appropriate form, though in one embodiment, they may mimic thestructure of the rotational couplings of the passive lateral arms 344 inthat each of the first and the second ends 356, 358 may form a receiver360 configured to receive a corresponding protrusion 362 extending fromthe battery housing 270 and from the lateral actuation gearbox housing342, respectively, via a friction fit.

After the lateral drive arms 354 are attached, the K-wire 214 and thelower coupling device 242 may be removed, as shown in FIG. 23 (FIG. 35B,532), followed by the dilator 202, as shown in FIG. 24 (FIG. 35B, 534).

After removal of the K-wire 214, the lower coupling device 242, and thedilator 202, a lateral retraction assembly 370, which, in thisembodiment, may include the handle 310, the lateral actuation gearbox308, the opposing passive lateral arms 344, and the opposing lateraldrive arms 354, may be employed to separate or laterally retract theblade subassemblies 240 from a closed position 390, shown in FIGS.25-27, to a retracted position 392, shown in FIGS. 28-31 (FIG. 35B, 524,536).

In further detail, FIG. 25 illustrates a perspective view of the lateralretraction assembly 370 having an open housing 342 of the lateralactuation gearbox 308 to detail one embodiment of the mechanics of thegearbox 308. In this embodiment, the handle 310 may incorporate a wormgear 372 at its distal end. The worm gear 372 may be positioned betweenand enmeshed with two opposing lateral gears 374, one bordering eitherside of the worm gear 372. Each of the lateral gears 374 may include apivot point 375 about which the remaining components of the gear 374rotate, a teeth portion 376 that engages with the worm gear 374, and adrive portion 378 containing a protrusion 362 configured to frictionallyfit within the receiver 360 of the second end 358 of one of the lateraldrive arms 354.

The teeth portion 376 of each of the lateral gears 374 may have avariable radius that extends between the pivot point 375 and the teethportion 376. The variable radius may increase from a first radius, r₁,located at a first end 380 of the teeth portion 376 to a larger secondradius, r₂, located at a second end 382 of the teeth portion 376.

In actuating the lateral retraction assembly 370 (FIG. 35B, 536),rotation of the worm gear 372 via the handle 342 causes the enmeshedteeth portions 376 of the opposing lateral gears 374 to travel from thefirst ends 380 engaged with the worm gear 372 at the smaller radius, r₁,to the second ends 382 engaged with the worm gear 372 at the largerradius, r₂. This travel causes the lateral gears 374 to pivot about thepivot points 375, such that the drive portions 378 of the gears swingoutward in the direction of arrow B as the radius of each lateral gear374 increases from r₁ to r₂. This outward trajectory, in turn, drivesthe lateral drive arms 354, and thus the connected blade subassemblies240, in the outward direction of arrow B, from the closed position 390of FIGS. 25-27 to the retracted position 392 of FIGS. 28-31.

Before, after, or at increments during the process of actuating thelateral retraction assembly 270 (FIG. 35B, 536), and as discussed abovein relation to FIGS. 11-13, the wing actuation assembly 290 of eachblade subassembly 240 may be employed to adjust the adjustable wings 252from the open position 280 parallel with the blades 244, shown in FIGS.25-27, the closed position 282 perpendicular to the blades 244, shown inFIG. 30, and any position therebetween, such as the angled position(e.g., 27 degrees relative the blade 244), shown in FIGS. 28-29 and 31(FIG. 35B, 538). In this regard, the two opposing blades 244 aresufficient for lateral retraction, without the need for additionalblades as required by existing retractor systems, as the adjustablewings 252 prevent creep of the muscle between the blades 244 and intothe surgical pathway 114 during retraction. Throughout the steps ofrotating the dual-blade assembly 230 from the insertion orientation 239to the rotated orientation 306 (FIG. 35B, 516), laterally retracting theblade subassemblies 240 from the closed position 390 to the retractedposition 392 (FIG. 35B, 524), and adjusting the adjustable wings 252between the open position 280 and the closed position 282 (FIG. 35B,538), the active monitoring tips 256 and 283 of the blades 244 and thewings 252, respectively, may be used to provide real-timeneuromonitoring to prevent impingement and/or encroachment upon adjacentnerve structures (FIG. 35B, 542).

FIG. 32 illustrates a perspective view of a fully assembled lateralretractor system 200, including all of the components, assemblies, andsubassemblies discussed above. In addition and in this embodiment, thehousing 342 of the lateral actuation gearbox 308 may incorporate a level384 to assist in positioning components of the system 200 when carryingout the disclosed method 500 of creating a surgical pathway 114 usingembodiments the lateral retractor system 200, as provided in FIG. 35.The level 384 may be calibrated to level the system with respect to thefloor, the surgical table 233, or any appropriate reference plane.Relying on the level 384 for partial positioning reduces the amount ofreal-time x-ray technology (e.g., fluoroscopy) required to locate thesystem 200 during operation, resulting in less radiation exposure to thepatient, the surgeon, and everyone else in the operating theater. In oneembodiment, the level 384 may be a bubble or spirit level, or the levelmay be a gyroscope.

Once the lateral retraction assembly 270 has been employed to retractthe blade subassemblies 240 to form the surgical pathway 114, thesurgeon may access the spine 100 (FIG. 35B, 540) via the resultingsurgical pathway 114, leveraging the LED lights 254 illuminating thesurgical area 266 as desired, as shown in FIG. 33, and observing theimages transmitted from the surgical area 266 via the video output 278from the video cameras 276, as shown in FIG. 34.

Each of the components that form embodiments of lateral retractor system200 discussed above may be formed of any appropriate conductive ornonconductive, autoclavable or otherwise sterilizable metal or plasticusing any appropriate manufacturing method. As discussed, somecomponents may be disposable to improve efficiency and customizabilityand reduce the possibility of disease transmission, while others may bereusable and sterilizable.

Embodiments of the lateral retractor system 200 provide three separatekinds of movement—rotation of the single-component dilator 202 and thedual-blade assembly 230 from the insertion orientation 239 to the finalrotated orientation 306, rotation of the adjustable wings 252 from theopen position 280 to the closed position 282, and retraction of theblade subassemblies 240 from the closed position 390 to the retractedposition 392—that allow for a more sophisticated initial placement ofthe single-component dilator 202 and the dual-blade assembly 230 in amanner parallel to the psoas muscle 102 and, therefore, less damaging tothe muscle and nerve structures adjacent to the patient's spine. Ratherthan crushing or trapping sensitive body tissues beneath the dilatorand/or the blade assembly, the disclosed lateral retractor systemenables embodiments of the dilator 102 and the dual-blade assembly 230to bypass those tissues and instead “separate” them to create thesurgical pathway 114, as desired, with the use of an elegant design thatfeatures only two blades. In addition, rotation of the flat, narrowdilator 202 allows the dilator 202 to separate the psoas muscle tissueswithout the need for a more complicated series of progressively largercircular dilators, as required in the prior art.

Further, built-in lighting and video capabilities provide the surgeonwith streamlined and flexible lighting of the surgical area and theability to view his or her actions without hunching over the patientand/or the surgical apparatus. Detachable and disposable distal bladeportions and adjustable wings allow the system to accommodate anypatient physiology and can be selected in the operating theater asdeemed necessary by the surgeon. In sum, the unique lateral retractorsystem allows for a lateral approach to the spine to be made in a moresafe and efficient manner for the patient and for the surgeon.

In addition, continuous, real-time neuromonitoring via the activeneuromonitoring tips 222, 256, and 283 located at the distal ends of thedilator 102, the blades 244, and the adjustable wings 252, respectively,further assists in reducing damage to the patient's nerves and plexus inthat the system may continuously monitor, and avoid, impingement orencroachment upon nerve structures within a 360-degree monitoring rangeabout the circumference of the system 200. This continuousneuromonitoring occurs throughout the process of forming the surgicalpathway 114 and any subsequent surgical procedure.

In one embodiment shown in FIGS. 36A-36B, a dilator 202 a may besubstituted for the dilator 202, discussed above, to provideneuromonitoring capabilities free of internal wires. In this embodiment,the dilator 202 a may be formed of a conductive material such as, forexample, aluminum and may leverage the internal conductivity of thedilator's rectangular body 204 a to form a conductive electrical pathway205 between one or more conductive input surfaces 207 formed at aproximal end 206 a of the rectangular body 204 a and a conductive activemonitoring tip 222 a disposed at a distal end 208 a of the rectangularbody 204 a.

In this embodiment, the electrical pathway 205 may be configured viaselective shielding applied to portions of the dilator 202 a. Forinstance, dilator surfaces intended to be nonconductive, insulatedsurfaces may be coated with an insulative or nonconductive layer. In oneembodiment, a portion of an outer surface 211 of the aluminum body 204 amay be coated with an anodized layer 213, which may be nonconductive andalso provide a hardened surface that resists scratching and other damageto the dilator 202 a. In one embodiment, a non-stick material such asTeflon may be added to the anodization to render the anodized layer 213“slippery” such that the dilator 202 a more easily glides relative toother system components and/or bodily tissues during the insertion andremoval processes.

In applying the anodized layer 213, portions of the outer surface 211that are desired to be free of anodization, and thus conductive, may bemasked during the anodizing process. In this embodiment, the conductiveinput surfaces 207 and the active monitoring tip 222 a may be maskedsuch that those surfaces remain conductive in their entireties. Thus,when an electrical signal is applied, through the monitoring cable 224(FIG. 8) or otherwise, to the dilator 202 a at the conductive inputsurfaces 207 at the proximal end 206 a of the dilator 202 a, the signaltravels via the conductive electrical pathway(s) 205 to the activemonitoring tip 222 a, which spans 360 degrees of the distal end 208 a ofthe dilator 222 a.

Impingement or encroachment of the active monitoring tip 222 a upon oneor more nerve structures causes the nerve structures to fire andgenerate a responsive signal, which is conducted back through theelectrical pathway(s) 205 to the monitoring cable(s) 224 incommunication with the electrical pathway(s) 205 at the conductive inputsurfaces 207, thereby translating the neurosensing stimulation of theactive monitoring tip 222 a to external monitoring equipment (not shown)via the monitoring cable 224 and determining, in real time, with 360degrees of monitoring range, and with an internal-wire-free mechanismthat is more simply and cost-effectively manufactured, a possibility ofnerve or plexus injury as the dilator 202 a is inserted (FIG. 35A, 508).

In a manner similar to the dilator, the blades and the adjustable wingsmay also be configured for continuous, real-time, 360-degreeneuromonitoring that does not require a wired electrical pathway withintheir components. FIGS. 37A-37F illustrate front, rear, and numerouspartial views of an exemplary embodiment of a blade 244 a, hingedlybordered by two opposing adjustable wings 252 a. In operation and in oneembodiment, the blade 244 a and the wings 252 a may be electivelysubstituted for the blade 244 and the wings 252 described above. In thisembodiment, the blade 244 a and the wings 252 a are similar to the blade244 and the wings 252, discussed above, in both structure and function,and additionally feature no-wire neuromonitoring capabilities similar tothe dilator 202 a, discussed above in relation to FIGS. 36A-36B.

In further detail and as shown in FIGS. 37A-37B, the blade 244 a mayhave a proximal blade portion 246 a, a detachable, disposable distalblade portion 248 a, and opposing longitudinal edges 250 a that extendbetween a proximal end 260 a of the proximal blade portion 246 a and adistal end 255 a of the distal blade portion 248 a. The opposingadjustable wings 252 a may be hingedly coupled with each of the opposinglongitudinal edges 250 a via a plurality of hinge pins 249, as shown inFIGS. 37A-37B.

In this embodiment, all components forming the blade 244 a and theadjustable wings 252 a, including the proximal blade portion 246 a, theremoveable and disposable distal blade portion 248 a, the wings 252 a,and the hinge pins 249, may be formed of a conductive material such as,for example, aluminum and may be strategically coated with anonconductive, insulated layer such as an anodized layer 271 so as toform an internal conductive electrical pathway 253 through the multiplecomponents. In this regard, the proximal portion 246 a of the blade 244a may include at least one conductive electrical connection point,conductive input surface, or “jack” 251, shown in FIGS. 37C-37D, and thedistal portion 248 a of the blade 244 a and the opposing adjustablewings 252 a may each terminate distally in respective active monitoringtips 256 a, 283 a similar to the active monitoring tip 222 a of thedilator 202 a. As shown in FIGS. 37E-37F, select surfaces of theproximal blade portion 246 a and the distal blade portion 248 a may bemasked so as to form adjacent and contacting electrically conductivesurfaces 257, 259 when the proximal and distal blade portions 246 a, 246b are assembled together.

In operation, the electrical connection point 251 may act as an inputpoint where electrical conduction initiates, via the monitoring cable224 or another appropriate source, such that an applied electricalsignal conducts from the electrical connection point 251, through theproximal blade portion 246 a, to and through the wings 252 a via thepins 249, to and through the distal blade portion 248 a via theconductive surfaces 257, 259, and through the active monitoring tips 256a, 283 a along the conductive electrical pathway 253 shown in FIG. 37B.This stimulus of the active monitoring tips 256 a, 283 a causes nearbynerve structures to fire and generate a responsive electrical signal,which may in turn be conducted back from the active monitoring tips 256a, 283 a to the electrical connection point 251 and to the monitoringcable 224 in electronic communication with external monitoringequipment, thereby sensing the stimulation of the active monitoring tips256 a, 283 a caused by proximity to nearby nerve structure(s) in realtime and with 360 degrees of monitoring range or field of view about anentirety of the distal ends of the blade 244 a and the wings 252 a.Thus, via the active monitoring tips 256 a, 283 a of each of the distalblade portions 248 a of the blades 244 a, continuous real-timeneuromonitoring may be performed to prevent nerve or plexus injury whenthe blade assembly 230 is inserted over the dilator 202 a (FIG. 35A,512, 514), as well as when the blade assembly 230 is rotated (FIG. 35A,516) and/or laterally separated or retracted (FIG. 35A, 524), asdiscussed above. Unlike existing systems, neuromonitoring over a full360-degree monitoring range may continue throughout the procedure.

Due to the multi-component nature of the wings as assembled to theblade, the internal conductive electrical pathway 253 avoids thecomplexity of a design which routes a wired pathway to the activemonitoring tips 256 a, 283 a, allowing for a more streamlined instrumentwith fewer components that is more efficient and less expensive tomanufacture.

Although the above embodiments have been described in language that isspecific to certain structures, elements, compositions, andmethodological steps, it is to be understood that the technology definedin the appended claims is not necessarily limited to the specificstructures, elements, compositions and/or steps described. Rather, thespecific aspects and steps are described as forms of implementing theclaimed technology. Since many embodiments of the technology can bepracticed without departing from the spirit and scope of the invention,the invention resides in the claims hereinafter appended.

What is claimed is:
 1. A lateral retractor system for forming a surgicalpathway through a plurality of psoas muscle fibers to a patient'sintervertebral disc space, comprising: A planar dilator for traversingthe plurality of the psoas muscle fibers, the planar dilator including:a conductive body defined by opposing flat surfaces that extend betweena proximal end and a distal end; a first nonconductive layer disposedupon an outer surface of the conductive body; a first activeneuromonitoring tip protruding from the distal end of the conductivebody to a leading distal edge configured for insertion into theintervertebral disc space; and a first conductive electrical pathwayextending from a first conductive input surface at the proximal end ofthe conductive body, through the conductive body, and to the firstactive neuromonitoring tip such that an electrical signal applied to thefirst conductive input surface causes the first active neuromonitoringtip to simultaneously and continuously stimulate one or more nervestructures located adjacent to any portion of a circumference of thedistal end of the conductive body to assess for an encroachment of theplanar dilator upon the one or more of the nerve structures.
 2. Thelateral retractor system of claim 1, wherein the first activeneuromonitoring tip has a maximum active width that equals a width ofthe conductive body.
 3. The lateral retractor system of claim 1, furthercomprising a retractable dual-blade assembly having two opposing bladesubassemblies, each of the opposing blade subassemblies comprising: aconductive blade body having a planar inner-facing surface, anouter-facing surface, and opposing longitudinal edges extending from aproximal end to a distal end of the conductive blade body, theretractable dual-blade assembly configured to pass over the planardilator such that the planar inner-facing surfaces of the conductiveblade bodies contact the opposing flat surfaces of the planar dilator; asecond nonconductive layer disposed upon an outer surface of theconductive blade body; a second active neuromonitoring tip protrudingfrom the distal end of the conductive blade body; and a secondconductive electrical pathway extending from a second conductive inputsurface at the proximal end of the conductive blade body, through theconductive blade body, and to the second active neuromonitoring tip suchthat a second electrical signal applied to the second conductive inputsurface causes the second active neuromonitoring tip to simultaneouslyand continuously stimulate one or more nerve structures located adjacentto any portion of a circumference of the distal end of the conductiveblade body to assess for an encroachment of the distal end of theconductive blade body upon the one or more of the nerve structures. 4.The lateral retractor system of claim 3, wherein the second activeneuromonitoring tip has a maximum active width that equals a width ofthe conductive blade body.
 5. The lateral retractor system of claim 3,each of the opposing blade subassemblies further comprising anadjustable wing rotatively coupled with each of the opposinglongitudinal edges of the conductive blade body via at least oneconductive hinge, each of the adjustable wings configured to movebetween an open position parallel to the planar inner-facing surface ofthe conductive blade body and a closed position perpendicular to theplanar inner-facing surface of the conductive blade body, wherein eachof the adjustable wings comprises: a conductive wing body having aplanar inner-facing surface and an outer-facing surface extending from aproximal end to a distal end of the conductive wing body; a thirdnonconductive layer disposed upon an outer surface of the conductivewing body; and a third active neuromonitoring tip protruding from thedistal end of the conductive wing body, the second conductive pathwayextending from the second conductive input surface at the proximal endof the conductive blade body, through the at least one conductive hinge,through the conductive hinge body, and to the third activeneuromonitoring tip such that the second electrical signal applied tothe second conductive input surface causes the third activeneuromonitoring tip to simultaneously and continuously stimulate one ormore nerve structures located adjacent to any portion of a circumferenceof the distal end of the conductive wing body to assess for anencroachment of the conductive wing body upon the one or more of thenerve structures.
 6. The lateral retractor system of claim 5, whereinthe third active neuromonitoring tip has a maximum active width thatequals a width of the conductive wing body.
 7. The lateral retractorsystem of claim 5, wherein the first and the second conductiveelectrical pathways are free of conductive wiring.
 8. The lateralretractor system of claim 5, wherein the conductive body of the planardilator, each of the conductive blade bodies, and each of the conductivewing bodies are formed of aluminum.
 9. The lateral retractor system ofclaim 5, further comprising a rotation assembly operably coupled to theretractable dual-blade assembly, wherein: the rotation assembly isconfigured to rotate the planar dilator and the retractable dual-bladeassembly about a longitudinal center axis of the planar dilator from aninsertion orientation in which the opposing flat surfaces of the planardilator and the planar inner-facing surfaces of the conductive bladebodies are disposed parallel to a grain of the plurality of the psoasmuscle fibers to a rotated orientation in which the opposing flatsurfaces of the planar dilator and the planar inner-facing surfaces ofthe conductive blade bodies are disposed parallel to a plane thatlaterally bisects the intervertebral disc space; and the rotationassembly comprises a rotation gearbox operably coupled to theretractable dual-blade assembly, the rotation gearbox including a gearchain that, when actuated, rotates the planar dilator and theretractable dual-blade assembly about the longitudinal center axis fromthe insertion orientation to the rotated orientation.
 10. The lateralretractor system of claim 9, further comprising a lateral retractionassembly operably coupled with the retractable blade assembly, thelateral retraction assembly configured to retract the two opposing bladesubassemblies away from one another, wherein the lateral retractionassembly comprises: a lateral actuation gearbox operably coupled betweeneach of the two opposing blade subassemblies and a surgical table, thelateral actuation gearbox including a retraction gear chain; and a pairof lateral drive arms, each extending between one of the two opposingblade assemblies and the lateral actuation gearbox, wherein actuation ofthe retraction gear chain retracts the pair of the lateral drive arms,and thus the two opposing blade assemblies, away from one another.
 11. Adilation system for minimizing damage to a patient's psoas muscle fiberswhen forming a surgical pathway to an intervertebral disc space of thepatient's spine, the dilation system having a planar dilator fortraversing a plurality of the patient's psoas muscle fibers, the planardilator including: a conductive body portion comprising two opposingflat surfaces that extend between a proximal end and distal end; aninsulative coating overlaying the conductive body portion; and aconductive neuromonitoring portion extending distally from the distalend of the conductive body portion to a leading distal edge configuredfor insertion between the patient's psoas muscle fibers, wherein when anelectrical dilator stimulus is applied to the proximal end of theconductive body portion, the electrical dilator stimulus propagatesthrough the conductive body portion to the conductive neuromonitoringportion such that the conductive neuromonitoring portion simultaneouslystimulates one or more nerve structures located adjacent to any pointabout a circumference of the conductive neuromonitoring portion.
 12. Thedilation system of claim 11, wherein a maximum circumference of theconductive neuromonitoring portion equals a circumference of theconductive body portion.
 13. The dilation system of claim 11, furthercomprising: a retractable blade assembly comprising opposingdetachably-attached blades, each of the opposing detachably-attachedblades configured to be passed over the planar dilator on either side ofthe two opposing flat surfaces of the planar dilator, each of theopposing detachably-attached blades including: a conductive body portioncomprising a planar inner surface and an outer surface that extendbetween a proximal end and a distal end of each of the opposingdetachably-attached blades; an insulative coating overlaying theconductive body portion of each of the opposing detachably-attachedblades; and a conductive neuromonitoring portion extending distally fromthe distal end of the conductive body portion of each of the opposingdetachably-attached blades to a leading distal edge of each of theopposing detachably-attached blades, wherein when an electrical bladestimulus is applied to the proximal end of the conductive body portionof each of the opposing detachably-attached blades, the electrical bladestimulus propagates through the conductive body portion to theconductive neuromonitoring portion of each of the opposingdetachably-attached blades such that the conductive neuromonitoringportion of each of the opposing detachably-attached bladessimultaneously stimulates one or more nerve structures located adjacentto any point about a circumference of the conductive neuromonitoringportion of each of the opposing detachably-attached blades.
 14. Thedilation system of claim 13, wherein a maximum circumference of theconductive neuromonitoring portions of the opposing detachably-attachedblades equals a circumference of the conductive body portions of theopposing detachably-attached blades.
 15. The dilation system of claim13, further comprising: an adjustable wing hingedly attached to eachlongitudinal edge of each of the opposing detachably-attached blades,each of the adjustable wings comprising: a conductive body portioncomprising a planer inner surface and an outer surface that extendbetween a proximal end and a distal end of each of the adjustable wings;an insulative coating overlaying the conductive body portion of each ofthe adjustable wings; and a conductive neuromonitoring portion extendingdistally from the distal end of the conductive body portion of each ofthe adjustable wings to a leading distal edge of each of the adjustablewings, wherein when the electrical blade stimulus is applied to theproximal end of the conductive body portion of each of the adjustablewings, the electrical blade stimulus propagates through the conductivebody portion to the conductive neuromonitoring portion of each of theadjustable wings such that the conductive neuromonitoring portion ofeach of the adjustable wings simultaneously stimulates one or more nervestructures located adjacent to any point about a circumference of theconductive neuromonitoring portion of each of the adjustable wings. 16.The dilation system of claim 15, wherein a maximum circumference of theconductive neuromonitoring portions of the adjustable wings equals acircumference of the conductive body portions of the adjustable wings.17. The dilation system of claim 15, wherein the conductive bodyportions and the conductive neuromonitoring portions of the planardilator, the opposing detachably-attached blades, and the adjustablewings are formed from aluminum.
 18. A retraction system for forming asurgical pathway through a patient's psoas muscle to the patient'sintervertebral disc space, comprising: a planar dilator for traversing aplurality of fibers of the patient's psoas muscle, the planar dilatorhaving a dilator body portion with opposing flat surfaces and a dilatorneuromonitoring portion extending distally from the dilator bodyportion; a dual-blade retractor having opposing retractable blades, eachof the opposing retractable blades configured to pass over the planerdilator such that each of the opposing retractable blades contacts oneof the opposing flat surfaces of the planar dilator, each of theopposing retractable blades having a blade body portion and a bladeneuromonitoring portion extending distally from the blade body portion,wherein: the planar dilator and each of the opposing retractable bladesare conductive such that an electrical dilator stimulus applied to thedilator body portion propagates to the dilator neuromonitoring portionand an electrical blade stimulus applied to the blade body portion ofeach of the opposing retractable blades propagates to each of the bladeneuromonitoring portions to simultaneously and continuously stimulateone or more nerve structures located adjacent to any portion of acircumference of the dilator neuromonitoring portion and any portion ofa circumference of each of the blade neuromonitoring portions to assessfor an encroachment of the planar dilator and the dual-blade retractorupon the one or more of the nerve structures.
 19. The retraction systemof claim 18, the dual-blade retractor further comprising an adjustablewing rotationally coupled to each longitudinal edge of each of theopposing retractable blades via at least one hinge mechanism, each ofthe adjustable wings having a wing body portion and a wingneuromonitoring portion extending distally from the wing body portion,wherein the electrical blade stimulus applied to the blade body portionof each of the opposing retractable blades propagates to each of thewing neuromonitoring portions to simultaneously and continuouslystimulate one or more nerve structures located adjacent to any portionof a circumference of the wing neuromonitoring portions to assess for anencroachment of the dual-blade retractor upon the one or more of thenerve structures.
 20. The retraction system of claim 19, furthercomprising an insulative dilator coating disposed upon the dilator bodyportion, an insulative blade coating disposed upon each of the bladebody portions, and an insulative wing coating disposed upon each of thewing body portions.